The present invention relates generally to subscriber side communications and more specifically to a software defined communications interface that accommodates changes in communications protocol from a centralized location rather than at the subscriber""s physical connection.
Often, the deployment of new communications technology places a burden on the subscriber to update their software and hardware in order to keep pace with current communication standards. For example, data communications over twisted pair wiring has resulted in a push for faster modems and improved signaling protocols compatible with the public switch telephone network. At present, analog modem technology is capable of transmission speeds close to 56 kbps which provides a boost in performance from the previous standard of bi-directional 36.6 kbps. The result has been the introduction by U.S. Robotics, Rockwell and other manufacturers of xe2x80x9c56Kxe2x80x9d modems.
Other examples includes the emerging variety of xDSL communications protocols including asymmetric digital subscriber line (ADSL), symmetric digital subscriber line (SDSL), high bit rate digital subscriber line (HDSL), and very high rate digital subscriber line (VDSL). Each xDSL variant represents a different transmission speed over a different distance of copper pair wiring. In order to take advantage of the protocol, the subscriber must obtain the appropriate application programs and hardware facilities that enable the signaling protocol to be applied in the channel coupling the subscriber to their service of choice. Often, the line circuits servicing the subscriber must be updated, modified or replaced through hardware and/or software changes.
Thus, while new communications standards can be implemented without modifying the internal wiring in a customer""s home or business, the communication equipment that enable such protocols must be updated, modified or replaced in order to implement the standard.
Apart from changes to the subscriber""s equipment, the introduction of new protocols also dictate changes in the call exchange facilities provided to service subscribers within a given geographic area. Typically a digital loop carrier (DLC) system is provided to handle the loop connections extending from subscriber to the call exchange facility in a subscriber area. Local loops of twisted pair copper wiring extend from the subscriber premise or customer premise equipment to the DLC. The DLC, in turn, is responsible for the routing calls placed by all subscribers in the service area to a centralized call exchange facility such as the local telco central office.
Originally, twisted pair wiring offered sufficient bandwidth for plain old telephone service (POTS) where frequencies stayed in the voice band of 300 to 3.4 kHz. Thus, DLCs could be designed to handle signaling within a relatively limited bandwidth compared to today""s standards. The introduction of new communications protocols with bandwidth requirements outside POTS and at many thousands of subscriber sites, however, means that large scale deployment can be prohibitively costly since the equipment must remain in place for years. In many situations, total replacement can be too expensive making deployment of new equipment in order to keep pace with new communications protocols impossible.
While prior art DLCs have become more flexible, each new protocol still requires a specific hardware design. In essence, each DLC contains interface and protocol specific hardware without satisfactory remote reconfiguration and bandwidth optimization to accommodate technology deployments.
The invention discloses a software definable DLC architecture based on high speed analog-to-digital (A/D) converters and digital signal processors capable of sampling to at least several MHz. Since each subscriber copper pair utilizes less than 1 MHz of bandwidth, multiple copper pair wires can be attached to a single DSP. Upbanding can be applied at staggered intervals so that all copper pairs reside in the distinct spectral bands. Signals arriving from a single copper pair can be sampled and digitized within the spectral band associated with each subscriber loop. The encoded digitized result can be transmitted back to the central office for decoding into the relevant signaling scheme according to the type of service attached to the subscriber. Preferably, the DSPs are reprogrammable so that subscriber upgrades are implemented more readily and more efficiently through a common media signal pathway. Updates in the customer premise equipment can be accomplished remotely through software deployed from a third party administration or maintenance facility, through the central office, or at the DLC.
According to one embodiment, a communications device for carrying signals from a subscriber to the centralized call exchange facility is disclosed. The communications device includes an interface to the subscriber and a signal processor coupled to the interface and configured to receive signals transmitted from the subscriber location. A second interface to a centralized call exchange facility is provided and arranged to receive processed signals from the signal processor. The communications device may also include a memory space storing a set of software algorithms that control the functionality of the signal processor. A digital-to-analog signal converter can be interspersed between the first interface and the signal processor to transform analog signals received from the subscriber to digital signals suitable for transmission to the centralized call exchange facility.
According to another embodiment, a software defined digital loop carrier (DLC) is disclosed. The DLC includes an interface to a plurality of subscriber lines with line circuits coupled thereto. The line circuits support the communications protocol utilized in each of the subscriber lines. The line circuits are programmable to accommodate modifications or deployment of new subscriber side protocols. The DLC also includes an interface to the trunk line leading to a centralized call exchange facility.
Each of the line circuits in the DLC includes an interface to a wire pair and a signal processor coupled to the interface and then configured to receive signals from a subscriber site. A second interface is provided between the line circuit and the trunk line leading to the centralized call exchange facility. A memory space such as Random Access Memory (RAM) or other similar electronic memory configuration is used to store a set of software algorithms that control the functionality of the signal processor associated with one or more of the wire pairs. In one embodiment, the software algorithms include instructions capable of implementing an xDSL protocol.
An advantage of the invention is that it allows flexible provisioning of services without hardware reconfiguration allocation or management thus reducing the overall cost of service changes and new service introductions.
Another advantage of the invention is that large scale deployment of new communications technology can be accomplished from a centralized location such as an operations or management facility or the local central office.
Still another advantage is that the same core DLC architecture can be utilized for more than one subscriber pair thus simplifying the call routing mechanisms servicing a group of subscribers.